Oral anticoagulant therapy in venous thromboembolism.

The main objective of treatment of venous thromboembolism (VTE) is the prevention of the extension, embolization, and recurrence of thrombosis. The long-term aim is to prevent late recurrences and the post-thrombotic syndrome. Heparin and oral anticoagulants (OACs) have been the cornerstones of VTE treatment in the last 30 years. Low molecular weight heparins (LMWHs) have been introduced more recently in the treatment of the acute phase of VTE, and they have allowed the home treatment of deep vein thrombosis (DVT) in selected cases. The optimal duration of OAC therapy after VTE is still controversial. Several studies have been conducted, and several are ongoing with the aim to stratify patients into risk categories for recurrence. Patients at high risk are candidates for long-term oral anticoagulation as the benefits of extended oral anticoagulation would outweigh the risk of bleeding. Patients are currently stratified into risk categories on the basis of clinical characteristics of the VTE event: (1) first or recurrent event; (2) idiopathic or due to a transient risk factor such as surgery, trauma, hormonal therapy, or immobilization; (3) presence of active cancer; (4) location (proximal DVT and/or pulmonary embolism, PE, or distal DVT); and (5) presence of known hereditary or acquired thrombophilia. Patients with distal VTE or VTE due to a transient risk factor are at a low risk of recurrence and short-term anticoagulation is indicated (3 months). Patients with an idiopathic event or with known thrombophilic defects such as FV Leiden or the G20210A prothrombin mutation are candidates for a longer course of therapy (6 months). Patients with cancer, antiphospholipid antibodies syndrome, recurrent idiopathic event, antithrombin deficiency, protein C or protein S deficiency, homozygosity for FV Leiden, and double heterozygosity are candidates for extended long-term anticoagulation. More recently, studies have indicated that other factors such as D-dimer levels after the discontinuation of OAC therapy or the residual vein thrombosis could be additional predictive factors for recurrences. In patients with VTE and cancer, oral anticoagulation poses a higher risk of bleeding, and such patients are more prone to recurrences. Alternative treatment with LMWH could be safer and more effective in these patients.